Sennheiser HD 660 S Over-Ear Open Headphones

I'll not wax poetic this time regarding the long and storied history and my experiences with the HD 6xx family of Sennheiser headphones. For that, simply go have a look at my "The Very Important Sennheiser HD 580, HD 600, and HD 650" review.

For now it's sufficient to state that the Sennheiser HD 600 and HD 650 are probably the most highly regarded enthusiast headphone in the world, and I highly recommend both. The HD 650 is a bit too warm sounding for me (just a bit), and the HD 600 is my favorite of the two.

The only problems with them is that the clamping force on the head is a little too strong, and they can sound a little "veiled" or distant in the lower presence region around 800Hz to 1500Hz—the HD 650 a bit more so than the HD600. Some will say the HD 650 has more mid-bass bloom, which it does, but it amounts to the same thing relatively speaking.

The clamping pressure can be modified fairly easily: extend the earpads all the way; grip the headband with both hands close to the center of the headband; then rotate your hands putting pressur near the center of the headband so as to stretch them out. The headband is a very high quality plastic and will not break; just be firm and not over-zealous feeling the plastic deform slightly as you do it and repeat until the pressure is right. I've heard others suggest to bend the metal headband extensions; I don't like this idea as the shape of the metal extensions are set to slide into pockets in the headband and I think it's best to let them retain their proper shape.

Numerous modifications have been developed by enthusiasts over the years. I have to review headphones in their stock form so I have only a little personal experience with these modified cans. If you'd like to learn more, I suggest starting your journey with this SBAF thread pointing to wide variety of HD 6xx information resources, and this post indexing a number of the modification threads.

And with that, we'll dive right into the HD 660 S

Sennheiser HD 660 S ($499.95)
The HD 660 S visually has very close family ties to its older siblings and, to me, it's the best looking variant yet. Liveried in simple matte black plastic with new grills that include a raised area with the Sennheiser logo it strengthens my personal conviction that audio gear should be black. Silly, I know, but I think a stealth black look helps put the focus on where it belongs: sound quality, not looks.


In this, and the following series of photos, the HD 600 is at left, the HD 650 at center, and the HD 660S is to the right.

The HD 660 S still has the somewhat tight clamping force, which can be remedied as mentioned above. Once set, the HD 660 S has the same quite comfortable, head-hugging fit and light weight of its predecessors. There are a few subtle differences.

Though the presentation case remains the same, the HD 660 S comes with two cables, both about ten feet long, one terminated in a 1/4" TRS plug, the other terminated in the new 4.4mm Pentaconn TRRRS balanced connector. Also included is a 1/4" jack to 3.5mm plug short cable adapter.


There has been a slight change to the earpad. From what I can gather the earpads are slightly thicker and have a slightly beveled inside circumference. In this Head-Fi post a Sennheiser representative said is was done to make them feel a little more "roomy and pleasant." I went back and forth between my HD 650 and the HD 660 S and felt indeed there might be a small improvement in comfort, but it is subtle.

Let's take a look inside:


As you can see there are a lot of similarities between the ear capsules of these headphones, if fact they are identical in a number of ways. Earpads, grills, and cables are interchangeable. The one big different is the driver assembly, which is completely different and not interchangeable. The diameter of the HD 600/650 driver housing is 1.722", the HD 660 S is 1.737" in diameter.


Close-up of the rear of the HD 650 driver (top) and the HD 660 S driver (bottom).

Obviously, these are quite different drivers. Rumors run rampant that this is an HD 700 driver. I wasn't able to find a definitive comment from Sennheiser, but in this post Jude claims it is a derivation:

The driver is based on the Sennheiser HD 700's driver, but it does not sound like an HD700 -- it sounds like an HD600-series headphone, through and through.

He's fairly privy to inside information, and a good hard look at the two make it fairly obvious they're related.


Rear of HD 700 driver (top) and the HD 660 S driver (bottom).

I don't have an HD 700 here to take physical measurements, but the resemblance is undeniable. The most distinguishing feature to my eyes is the very fine stainless steel mesh behind the outside edge of the driver formed to mimic the shape and ventilate that area evenly. Here's what the Sennheiser HD 660 S product page says:

The HD 660 S features a new transducer design developed by Sennheiser. This results in improved control of the diaphragm movements thanks to a specially manufactured precision stainless steel fabric, which is adapted to the contour of the diaphragm. Extremely light aluminum voice coils ensure the highest impulse fidelity.

Hm. Well they sort of state that it's a new design, but I'm betting that's a bit of poetic license—the HD 700 is a relatively new design. Thing is, impedance and phase measurements are almost identical.


Man, it doesn't get much closer than that. By my reckoning, it seems very likely that the HD 660 S is using the HD 700 driver design with a redesigned outer housing to fit into slightly changed HD 6xx baffle plate.


300Hz square wave response of the HD 600 (top), HD 660 S (middle), and HD 700 (bottom).

The thing to me that's very interesting is that, assuming it is an HD 700 driver, how little the driver performance itself effects the performance of the headphone as a whole. In the 300Hz square wave responses above you can clearly see the HD 660 S response (middle) is very much like the the HD 600 response (top) and is quite unlike the HD 700 response (bottom)...and that's a very good thing. I found the HD 700 a very bright headphone with an uncontrolled treble. Just goes to show you how much the overall acoustic of a headphone is largely due to the acoustics of the ear cup and has less to do with the driver itself.

Alrightythen, let's have a listen.

Sennheiser USA
1 Enterprise Dr.
Old Lyme, CT 06371
(860) 434 9190

donlin's picture

Very clear and honest. It’s refreshing to have a well known reviewer that doesn’t love everything. Sounds like there may be a rush to get the last 650’s.

Maybe's picture

The 660S is rather boring. I was excited at first but I got Sennheiser'ed.

Performance was to be expected given that the HD 700 and the HD 650 use transducers with almost identical TS parameters.
I'm sure if you were to stick an HD 599 driver inside a 650 it would sound similar aswell.

Used HD 580s for 150€ with new pads seem preferable.
However, I think I'll buy the 660S grills for my 650. Looks neat.
The closed HD 800 is next on the list. Then the new Baby Orpheus. And maybe they'll do something completely new in 10 years.

MikeC20's picture

I am a headphone enthusiast but I started with my obsession with High Fidelity home audio, the headphone to me is 100% based on trying to get the best sound possible while being the most convenient.

I still havent fallen in love with any bluetooth so I am fine dealing with the discomfort of cords, but I have been wanting the HD650 but with the inconvenience of needing an amp to really enjoy makes it something that I would never use as I would rather listen to my home audio if I have to be stationary.

My currenty heavy in use headphones are the se535, HD558, AKG 553 MKII and one of my favs the AKG K240 (what a high value headphone!).

My question is, is the 660S is a significant upgrade over the 558/598 headphones? If so I may have a must buy.

MikeC20's picture

Great job as always Tyll, thank you for doing such great work over the years!

metal571's picture

Actually any of the 600, 650, and 660S would be an upgrade over the 558/598 series. The only thing you will lose is soundstage width, and also the signatures are a bit less bright and aggressive in the upper mids and treble region. Detail however is significantly improved vs the 5x8 stuff.

jaredjcrandall84's picture

Based upon reviews, yes it is, but apparently the 650 is better than the 660s, so go there instead.

metal571's picture

Did you buy brand new pads for your 600 and 650 units immediately before doing this review? If not, that has enormously colored your perception of these models' sound signatures. It is well known that older pads will give your 600 and 650 that "smoother" and more "organic" sound that you mentioned. As soon as the pads are replaced, the sound is significantly changed. I would like to hear full follow-up impressions and see measurements of all of these 3 units once you have replaced all pads, if that was not done already, for the sake of everyone who is going to buy pairs of these headphones brand new.

ericw's picture

Agreed. Rin Choi measured a HD 650 with old and new pads, and switching from old to new pads increased 5-6kHz by more than 5dB, and generally everything above 1kHz got tilted up.

see: (scroll down to "Discussion")

I'm not sure if those measurements have been repeated elsewhere?

metal571's picture

Solderdude also looked into this a bit, talking about older style 650 pads vs newer ones, in addition to pad condition.

crazywipe2's picture

All the Headphones Tyll uses for comparison are in almost brand new condition. He is more than 25 years working with headphones giving a huge contribute to all the Headphone World. Do you really think he messed up the review because of the pads? Man, this is ridiculous and disrespecful, you are not talking with a noob.

Tyll Hertsens's picture
The 600/650 I use are relatively new, maybe 4-5 years old. You have to remember I only use them for comparative purposes, so I would guess both pair have less than 40 hours on them. The pads appear in very good shape.
zobel's picture

grainy A moderate texturing of reproduced sound. The sonic equivalent of grain in a photograph. Coarser than dry but finer than gritty.

What causes a transducer to produce grain?

amartignano's picture

Although I don't ear this increased graininess when comparing my 660S to my 600 (indeed I ear the 660S to sound more "organic") I really appreciated this sincere review, as always.

gibtg's picture

Pads, schmads ... There's clearly evidence in the measurements that the treble responses differ from the past designs and I'd trust Tyll's ears to determine how those changes will effect the overall presentation of the headphone. That's why I'm here!

Excellent review once again Tyll!

pete111's picture

"But I'll also steer buyers towards the HD 600—or Massdrop HD 6XX if it becomes available again—as the better sounding alternative."
Letting people know that the 6xx are indeed available on Massdrop now, yes with a delay, but still... a 650 for 200 bucks...

zobel's picture

Is there a relationship here, really?
Aren't the factors that determine impedance in dynamic drivers
1) length of voice coil wire (L)
2) gauge of voice coil wire (AWG)
3) type of conductor in VC wire (what metal)
4) strength of magnetic field in VC gap (B)
5) acoustic and mechanical resonance (Ir)
6) acoustic and mechanical impedance (Imm)
7) voice coil geometry (underhung vs overhung)

Knowing of several examples of sound being improved by increased
sensitivity / lower impedances, rather than the opposite, I don't believe that design criteria (Sensitivity / impedance) is a determining factor in driver performance. Think, for one example, Sennheiser Amperior vs HD 25 II, even in aluminum for both. Requiring a separate special amplifier is becoming less and less popular.

Not to say that better amplifiers won't improve the sound of headphones, any headphones, sensitive or not. Not only are we moving away from chip amps in phones through a wire to the cans, but now it is the rage to be wireless, which involves inevitable signal degeneration. Compressed, lossy music files via Bluetooth to sensitive IC powered cans is the future, very sadly. It isn't the sensitivity of the cans that is the problem though.

Pdxsnap's picture

The introduction of this model does seem a bit odd. It could/should have been a slam dunk in just improving a little on a classic to build on its cult following. If they had just made a unit just appreciably bettter than the 600/650 there would be a large market in devoted followers in upgrading.
I wonder how much of the desire to drop impedance is the reason for the miss fire? I also wonder if there were heated debates within Sennheiser regarding the impedance and direction of this model. Time will ‘perhaps’ tell.

zobel's picture

For many of the reasons Tyll pointed to,these cans don't really cut the mustard anymore. None of them. Biggest problem...bass rolloff. Next to that, the veil..lacking low treble and high mids.

This is a failed attempt to address the real problems with these cans. I disagree that the Sennheiser HD 6XX Massdrop was such a deal. Personally I think AKG had a better can through Massdrop with the AKG K 7XX.

The fact that the housing of the drivers makes such a huge difference in sound points to how much differently we hear them with our various sized ears. I bet I fill a whole lot more of the cans cavity with my flappers than most do. The size,and shape of ear canals makes huge differences as well as hair, glasses (sometimes), head size (fit) it isn't too surprising that pairing drivers to the entire enclosure involved (cans and the individual wearing them) is critical and accounts for the varied responses from individual to individual.

Good review Tyll....very disappointing that after what, 17 years? Sennheiser hasn't made more progress.

potterpastor's picture

I consider the He-1 progress

pete111's picture

I have to say that after your comment I was quite surprised to look at the AKG's 7xx frequency response... AKG are not exactly known for their deep bass. I agree with you that this roll off at 100 is kinda... Well there's something missing. What I was gonna say tough is that to get this bass, in a sub 500$ range, you have to either go closed, or planar, with the compromise associated with both these design and to me the 6XX is still very good value. But I was just thinking today that... Yeah, great classic, very good sound but I keep coming back to something with subs. My other cans are He-400is and Th-X00, which are both to me better than a 6 serie senn. but still more than twice the price of a Massdrop 6XX

zobel's picture

That Massdrop version of AKG's 7XX has improved bass over previous versions..another good result for Massdrop. It measures down 5 dB at about 17 Hz...not too shabby at all. It has all the clarity and detail, if not a tad extra presence, which is from 3.5 kHz to 6 kHz, (not as Tyll has it) that is sorely lacking in the HD 6XX series.

For example the HD 600 are down 5 dB at 40 Hz,(17 Hz for AKG) and down 10 dB at 5 kHz, compared to the AKGs which are flat at 5 kHz. It adds up to much better bass, and even better detail and presence. $200.00...a great deal.

I haven't heard the HiFiman,HE 400, but it sure measures well! The AKG looks has much more similarities to it than the Senns.

Your Fostex TH-X100 and the AKG K 7XX also measure remarkably similarly, with the Fostex looking a bit better in the sub bass, and
slightly recessed in the highs than HE 400, and the AKG K 7XX. I imagine they all three represent better values than the Sennheisers 6XX series.

I'm guessing that Tyll never listens with a subwoofer, just his little Harbeths, which roll off like the Sennheisers, so it is understandable that he doesn't miss the bottom octave as much as people with flat systems. I design and build loudspeakers, and have been now for 27 years (seriously...with good measuring tools) and am spoiled by having flat in room response. Which do you prefer your HiFiman or Fostex?

pete111's picture

Thanks, I like them both. I really like the punchy and dynamic sound of the Fostex, definitely have more slam but the Hifiman 400is could be called more neutral and with a larger image. Objectively I think the Hifiman is the better headphone but (even tough hifiman marketing suggest that) they are hard to drive and need a decent amp... Nothing fancy but just something better than the output of a phone. I'm having great result with the Bluewave Get that I've designed and put to market... I know, probably deserve to be flagged for self promotion... but threw it in anyway, I'll take the blame if need be...

Phoniac's picture


amartignano's picture

No progress? You forgot hd800.

amartignano's picture

Moreover many find the hd660s an improvement over 600 and 650.

roscoeiii's picture

I think Tyll makes it quite clear the specific reason he prefers the 650, 6XX, or 600. Of course the relative importance of various aspects of audio gear differs from person to person (for example, soundstage isn't especially crucial to my audio decisions). It is very easy to imagine someone preferring the 660S based on aspects of it compared to the 650/6XX/600 that this review describes.

I very much appreciate how Tyll contextualizes his own personal preferences in his reviews. And in many cases will not review a pair of headphones (bright/treble heavy) that go against those preferences. Sometimes we gravitate towards reviewers whose taste in gear reflects our own. In other cases, we must triangulate our tastes with the reviewer's and hope that the review has enough detailed description to allow us to do that.

I hope that in the comments those who prefer the 660S also extend us the favor of giving their reasons why. Let's not forget the role that personal preferences play in this hobby.

amartignano's picture

I want to specify that I really appreciate Tyll reviews and opinions even when my sensation are different. I wrote a long post about my impressions on the 660S on headfi, and I will not repeat here :p It's not my preferred headphone, I like my hd800S more, and I might also prefer my hd700 on the hd660S. Nevertheless I like the 660S and this time I disagree not only in the preferences (obvious because we are all different) but also in some audio facts, which is strange as I always agree with Tyll on the "facts". For example, like others I find the hd660S to have less grain than the hd600, not more.

amartignano's picture

More specifically, there's a thing of the hd660S that really mesmerized me, that it's not mentioned in the Innerfi's review. It's the wonderful work on timbre and harmonics of cymbals and triangles that the hd660S does. It really surprised me. The hd600 in direct comparison seemed quite "muted" on high cymbals and triangles.

BoyBalastog's picture

I generally assume that because Tyll tends to dislike strong treble that he percieves a hard edge on the upper frequencies as being grainy because of how harsh it sounds to him, rather than because there's any actual obscurity of detail. I get what he means when he says that being detailed and resolving isn't the same as merely having elevated upper mid and treble response, but his own preference towards smooth resolve over bright resolve is evident. Some people, including me, prefer to have actual presence of detail while having a bright edge to the upper frequencies to accentuate it.

But on the other hand, I once did hear an HD700 and I really did hear a grainy fuzz to it, but in a way that was markedly different from the very veiled (to me at least) HD650. I've only tried it once admittedly, but it left a bad impression. So I'm not all too surprised that Sennheiser may have fumbled a bit in trying to stuff the HD700's drivers into a 600 series shell to try and make for a lower impedance model.

Phoniac's picture


Phoniac's picture

I did not post this here - the buggy software did...

potterpastor's picture

Appreciated the heartfelt review.
Hopefully in years to come, some of that HE-1 awesomeness will trickle down to the 600/700 series.

I really enjoy the HD 579, the older brother of the 569

MattTCG's picture

I agree with some of your review but there are some issues that we are quite far apart on. Just want to say that its a mistake to suggest bending the headband in the middle. You'll have a contingent of hobbyist emailing you after the headband assembly snaps in two. ONLY stretch the metal section...imo.

amartignano's picture


Tyll Hertsens's picture
Sennheiser has a GREAT materials science lab. I've been relieving the pressure of these headphone in the way I described for...what, 20 years. Never oncehave they felt like they were getting anywhere near fracturing or even fatiguing the material. Don't ham-fist it for sure; feel what's going on. But bending the metal headband extensions will change their shape, and that shape is designed for that pocket in the headband.
GNagus's picture

Senn is replacing a headphone for an new and "improved" version instead of complimenting the HD650 with an easier to drive version. I have some theories why:

1) The HD650 isn't selling as well as Sennheiser would like, when there is the 600 selling for less (MSRP prices).

2) The HD700 is not selling well and Sennheiser created a new headphone using HD700 parts from the parts bin (driver, etc)

I'm disappointed, but only that the HD650 will be discontinued.

darkswordsman17's picture

The pad differences could be interesting. Actually, Tyll did you try swapping the 660 pads with 650/600 ones to see if that alone might offer the subtle sound differences, or even just a change?

Another thing that would've been interesting, and granted them not including a 3.5mm cable seems to indicate they don't expect it in spite of their reasoning of making it more efficient, but a comparison out of portable players I think would be fairly important. The thing is, I'd almost guess that they'd actually be worse (with regards to smoothness), but perhaps that's the desire, or the bass blooms up more which is what more people would want. Or maybe after processing that might be typical on such devices, that the treble is enjoyed (basically it helps retrieve some of that lost that causes say the HD650 to sound too veiled)?

zobel's picture

Summary Table
Frequency Range Frequency Values
Sub-bass 20 to 60 Hz
Bass 60 to 250 Hz
Low midrange 250 to 500 Hz
Midrange 500 Hz to 2 kHz
Upper midrange 2 to 4 kHz
Presence 4 to 6 kHz
Brilliance 6 to 20 kHz

zobel's picture

...many,if not most, would call upper midrange (2 to 4 kHz ) low treble, with treble being 4 kHz to 6 kHz...presence and air (or brilliance) from 6 kHz up.

I think we should all use the same (or close) definitions for what we are talking about, otherwise it is just babble.

sszorin's picture

@ zobel - Sub-Bass is 15/20 to 40Hz.
150 Hz and up are lower middle frequencies

zobel's picture
zobel's picture

Sub bass...............1o Hz to 25 Hz
Low Bass...............25 Hz to 50 Hz
Mid Bass...............50 Hz to 100 Hz
Upper Bass............100 Hz to 250 Hz
Low Mids..............250 Hz to 500 Hz
Midrange.............500 Hz to 2000 Hz
Low treble..........2000 Hz to 4000 Hz..(with presence 3kHz - 6 kHz)
Treble............4000 Hz to 10,000 Hz
Upper treble....10,000 Hz to 20,000 Hz..(same as air or brilliance)

Tyll Hertsens's picture

I go with the mothership. John Atkinson has all the ranges buried in the glossary here:

I think the human vocal range as a stand-in for where the mid-range is. For me, 150Hz to around 800-1000Hz. after that, overtones, spittle throat sounds, and consonant/sibilant sounds appear, which I think of as in the treble area.

The character of 'presence' occurs, in my opinion, in how well one can hear these upper glotteral and consonant making frequencies. Essentially, twig and branch snapping stuff. These sounds---maybe 800Hz-4kHz---are where our primal survival system triggers reside.

Emphasis will give you presence; de-emphasis will give you distance---muting through the trees, I'll offer. I consider that treble response.

I see it as:

Bass: 15Hz-150Hz
Mids: 150 Hz-1500Hz
Treble: 1500Hz-20kHz (That third of an octave up there don't hardly count.)

zobel's picture

I think that it will work for all practical purposes..even if not quite the norm, I think, from most of what I've seen elsewhere.

I think the presence range has almost always been listed no lower than 2kHz, and extending to 6kHz (usually), and maybe the reason for that is because those frequencies are above the fundamentals in music far enough to change the distance perceived to them more than simply the quantity of them. Think a distant branch snap, or grass rustling vs a close by one. Low frequencies travel much further than higher ones. We may hear loud rustling or snapping, but our distance cues are frequency based. When using EQ for playback or recording instruments...including the voice, the cues to distance are found in the low treble..3kHz to 6kHz. You can prove this to yourself by playing with the EQ in listening sessions. If upper mids (800 Hz to 2kHz) are raised in level, to most, I think, it only makes those tones louder, not closer. It is all subjective, of course, but this is one area where there is disagreement. No matter, really, if we are all on the same page.

Long time listener's picture

I agree that this looks right:

Sub bass...............1o Hz to 25 Hz
Low Bass...............25 Hz to 50 Hz
Mid Bass...............50 Hz to 100 Hz
Upper Bass............100 Hz to 250 Hz
Low Mids..............250 Hz to 500 Hz
Midrange.............500 Hz to 2000 Hz
Low treble..........2000 Hz to 4000 Hz..(with presence 3kHz - 6 kHz)
Treble............4000 Hz to 10,000 Hz
Upper treble....10,000 Hz to 20,000 Hz..(same as air or brilliance)

Someone on this site once defined "midrange" based on the frequency of middle C on the piano--failing to note that the piano is only a bass/midrange instrument. The keyboard does not present the full range of frequencies shown in Tyll's graphs, but only extends into the upper midrange or lower treble. Thus at about 256 or 260 Hz, middle C actually represents the transition from upper bass to lower mids--as shown in the post by Zobel.

Tyll, the presence region is roughly 2khz to 5khz. It's not for you to re-define according to your own predilections.

I'll be very happy if the above can be used as a reference.

zobel's picture

Bass.........20 Hz to 250 Hz
Midrange....250 Hz to 2500 Hz
Treble......2500 Hz to 20,000 Hz

This represents the range of Human hearing, and divides the frequencies into the old standards of Bass, Mids, & Treble. These have been the widely accepted definitions for many years.

In the table below, the further subdivisions are useful to more accurately describe the audible spectrum, which have developed over time, to describe the ten octaves we can hear as illustrated below. Note also the frequencies that most refer to as ("presence") and ("air" or "sparkle"). It is important that we use these standards in naming the different bands of frequencies in order to have a common language. If not referring to this standard, the only alternative is to talk in terms of the frequencies in Hz, and mention only the numbers.

Sub Bass...........10 Hz to 25 Hz
Low bass...........25 Hz to 50 Hz
Mid Bass...........50 Hz to 125 Hz
Upper Bass........125 Hz to 250 Hz
Low Mids..........250 Hz to 500 Hz
Central Mids......5oo Hz to 1000 Hz
Upper Mids.......1000 Hz to 2500 Hz
Low Treble.......2500 Hz to 4500 Hz ....('presence region'.....
Central Treble...4500 Hz to 10,000 Hz ...3 kHz to 6 kHz)
Upper Treble...10,000 Hz to 20,000 Hz .('air/sparkle' 10 kHz & up)

amartignano's picture

Anyway, I find the absence of listened music for the review a strong defect on this and other reviews (excellent for all other things). I almost never found an headphone always better than another with different recordings.

Phoniac's picture

You first said it correctly in your review, but then come up with thgis wring statement again:

No, the 660s is far from being loud enough on a usual smartphone like an iPhone.

Phoniac's picture

Ok, I give up. This software just too stupid.

coastman25's picture

Thank you Tyll for yet another exemplary review. Being late to the party has its rewards. You are able to comment on the rumours and previous badly made reviews.
I can only assume other reviewers of these phones took too much notice of the Sennheiser hype and swallowed it.
These phones seem to have been designed and made via a committee, with the marketing and sales departments having the biggest say. At best, they are an attempt to be all things to all people and failing to build on the HD 600 heritage. It is as if they do not know the value of what they already possess.
Hats off to you Tyll, for being so exacting and honest with your evaluation.

amartignano's picture

Have you ever heard the 660S? I ask because I have them, and I'm entitled to partially disagree with Tyll impressions. I really appreciate his opinions, but it's not the only "truth" in HiFi. The fact that he disagrees with others, doesn't mean that the others are dumb hypey fanboys.

coastman25's picture

Have you ever bought a fake product? The more you pay for it the less likely you are to question its authenticity. I think its called self justification. If you are happy with the HD 660s then I guess that's all that matters.
Happy listening.

amartignano's picture

Ok, you never heard the 660S.

coastman25's picture

My comments were about the quality of the review and the reviewer not the product. For that I don't need to hear the 660s. I trust the reviewers integrity he didn't just comment about the sound he went into detail about how Sennheiser's misleading hype, the drivers, how they measure like the 700's etc etc.
I have bought 3 headphones without first hearing them, just going by Tyll's reviews and I am not disappointed or have found myself disagreeing with his reviews.

amartignano's picture

The fact is, that many headphones enthusiast, me included, find the HD660S perfectly good as an hair of the hd580/6xx heritage. This is respectable like other opinions. And I strongly disagree with your assumptions about 660S creation and judgement about who likes this headphone. Here we say that you "did a lick"... but you never heard the headphone. To be clear: I always appreciate the quality of Tyll reviews, except for the absence of indications of the music played for the review.

coastman25's picture

So why don't you take up your complaints with the author of the review? I cannot help you. I am happy with the review your not.

amartignano's picture

I was mainly commenting about your post, so I wrote to you. Why write to Tyll about your post? :D

coastman25's picture

Well if you cannot read I guess there is no point in commenting at all!

amartignano's picture

And I've also bought headphones despite Innerfidelity reviews and liked them very much with my ears/tastes.

IgorC's picture

Interesting review. Thanks!

My first thought was that 660s had hand-picked 650s drivers (with better THD and FR characteristic.)

Well, it's actually HD 700 driver after all. Makes sense. Probably Sennheiser doesn't want to throw away some HD 700 drivers which don't meet THD requisites (<0.03%) but still suitable for HD660s (<0.04%)

I still remeber that my first audiophile grade headphones were HD 650. :) Awesome.

Impulse's picture

Welp, that settles it, I'd been curious about these for a little while but seeing as I have some decent upstream gear I guess I'll pass.

I've been wanting to hear the difference between the HD650 & my HD600, and/or mod the former while having a sort of reference, guess the time to do so is now before they vanish.

Hopefully they're still $300-ish in January after I'm done traveling for the holidays...

GimmeCans's picture

I want to echo the sentiment expressed by an earlier commenter, that it's good to know that Innerfi is willing to call things the way you see (hear) them, even when it doesn't 'tickle'. Manufacturers shouldn't expect a 'free ride'.

As a longtime HD650 owner and advocate, the review eased the tinge of buyer's remorse I felt when learning of the 660S just after buying the Beyer Amiron which is $100 more. Despite my high regard for Senn's classic, I'd be hard pressed to name an area where the Amiron doesn't outperform the 650 to my ears (maybe the 650's smoothness makes it a little more 'forgiving' on some material.) For those who were considering the now-discontinued 650 or another open can in that range, the Amiron should be on your radar IMO although I will admit the overall signatures are quite different.

GumbyDammit223's picture

Do you want a HD700 to compare against? I'm in Bozo so it would be quick to let you borrow mine.

GimmeCans's picture

Now comes the HD58xx from Massdrop, looking almost identical to the HD6xx. There's only one man who can sort all this out.... Look! Up in the air! It's a bird! It's a plane!

GimmeCans's picture

Oh, and it's $149....

Martin.'s picture

Saw this as well yesterday. Seems very interesting, would like to see someone review it. I also have just bought a 6xx from Massdrop cause of this review.

arteom's picture

Great review. I get the impression that manufacturers are designing their products to play well with low level gear like smartphones. Think they have come a long way with pulling that off while still having a sound that is above consumer level products and more in line with audiophile level. The compromise being how well they scale and the grain you spoke of. I think they are working hard to disguise the grain as 'energy up top'. It is remarkable that they have been able to achieve this at all, don't think we would have seen a product like this ten years ago. That all being said, I won't be trading in my 650 anytime soon.

verbosity's picture

Hy Tyll,

Would you say the 660s is superior to the HD600/650 when driven by a cheap <$300 amp? If so it seems an easy explanation for its existence and positive reception in the forums. If not, who knows... maybe just personal preference of most people deviates from your own in this case?

Michael Ford's picture

Thanks, Tyll. Great review as always. You've given me all the excuse that I need, and have been looking for a long time, to buy another HD650! I'll use one with a CH650S balanced cable on my HDVD800, and the other with the stock cable on everything else. I also have an early HD600 (and 580 Precision) and although I fully understand why you and many others prefer the HD600, my preference is for the HD650. To me it is warmer, and yes, darker, but it has better resolution and soundstage.

One thing I'm certain about is that if Senn do discontinue the HD650, it will immediately go from legendary status to cult status!

ScaryFatKidGT's picture

I think Sennheiser is running into the Gibson/Fender problem... they have been doing things so right for so long either by nailing it right away or through trial and research an actually being great or by customers just expecting that sound or a combination of the two that if they make anything different it doesn't do well. I think Sennheiser should have improved the HD700 with an "HD700 S" instead of making a 660 and then the Massdrop "580" which is more of a 660 in 580 skin.

detlev24's picture

Another quick review with comparison to the elder models; from another point of view. Enjoy!

blogkens's picture

These headphones are really very great.

blogkens's picture

if Senn do discontinue the HD650, it will immediately go from legendary status to cult status! Read more.

Michael Ford's picture

Tyll, for your information, I've just replaced the ear pads on my original (pre Jubilee model) precision 580's with replacement Sennheiser pads (part number 050635), and they are identical to the new pads on the 660 S, i.e. a little thicker and slightly bevelled on the inside. This leads me to assume that all 600 series headphones will now come with pads like this, and it's not a difference specific to the new 660 S.

Best regards, Michael.

Michael Ford's picture

I now see that the Senn rep stated (in the Headfi post that you linked) that the replacement parts would be the new design from now on, but, again, one would assume that means that new HD 600 and HD 650 headphones will also have the new pads. It wouldn't make any sense to manufacture two slightly different shape pads and provide the old type only on new HD 600/650's and not as replacements for those headphones. All pretty irrelevant in the bigger scheme of things, but nonetheless, good to know.....maybe......

poekimalu's picture

Hi, I have LCD2 Classic which I love it, but it gave me a headache most of the time because the weight and clamped to much near my ear. My question is should I get HD660S or HD650 if I decides to swap my LCD2 Classic? I did tried HD660S before but never try HD650. Cheers

smileday's picture

Could you check whether the isolation graph correct? 4-5 db isolation across the audio band from an open back headphone? HD600 and HD650 did not do that.

Luigi's picture

Sennheiser started to sell the 660 with the 58x name on massdrop. The difference between the two models are 350 dollars and a 10 cent of felt againist the back of the driver...